Derivative of 3cos^5x.

hi, my first post so pls be gentle!
HNC maths question driving me mad as must be doing something stupidly wrong.
3cos^5x is the question and result should be -15sinx cos^4x
i must be doing something fundamentally wrong as i cant match the answer given. any help greatly appreciated.

Last edited by mr fantastic; May 8th 2010 at 03:08 AM.
Reason: Re-titled.

hi, my first post so pls be gentle!
HNC maths question driving me mad as must be doing something stupidly wrong.
3cos^5x is the question and result should be -15sinx cos^4x
i must be doing something fundamentally wrong as i cant match the answer given. any help greatly appreciated.

... is the chain rule. Straight continuous lines differentiate downwards (integrate up) with respect to x, and the straight dashed line similarly but with respect to the dashed balloon expression (the inner function of the composite which is subject to the chain rule).
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Don't integrate - balloontegrate!

hi, my first post so pls be gentle!
HNC maths question driving me mad as must be doing something stupidly wrong.
3cos^5x is the question and result should be -15sinx cos^4x
i must be doing something fundamentally wrong as i cant match the answer given. any help greatly appreciated.